[PATCH] btrfs/194: add a test for multi-subvolume fsyncing

[Josef Bacik <josef@toxicpanda.com>]

From: Josef Bacik <jbacik@fb.com>

I discovered a problem in btrfs where we'd end up pointing at a block we
hadn't written out yet.  This is triggered by a race when two different
files on two different subvolumes fsync.  This test exercises this path
with dm-log-writes, and then replays the log at every FUA to verify the
file system is still mountable and the log is replayable.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 tests/btrfs/194     | 102 ++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/194.out |   2 +
 tests/btrfs/group   |   1 +
 3 files changed, 105 insertions(+)
 create mode 100755 tests/btrfs/194
 create mode 100644 tests/btrfs/194.out

diff --git a/tests/btrfs/194 b/tests/btrfs/194
new file mode 100755
index 00000000..d5edb313
--- /dev/null
+++ b/tests/btrfs/194
@@ -0,0 +1,102 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2019 Facebook.  All Rights Reserved.
+#
+# FS QA Test 194
+#
+# Test multi subvolume fsync to test a bug where we'd end up pointing at a block
+# we haven't written.
+#
+# Will do log replay and check the filesystem.
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+fio_config=$tmp.fio
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	$KILLALL_PROG -KILL -q $FSSTRESS_PROG &> /dev/null
+	_log_writes_cleanup &> /dev/null
+	_dmthin_cleanup
+	rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/dmthin
+. ./common/dmlogwrites
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs generic
+_supported_os Linux
+
+# Use thin device as replay device, which requires $SCRATCH_DEV
+_require_scratch_nocheck
+# and we need extra device as log device
+_require_log_writes
+_require_dm_target thin-pool
+
+_require_fio
+
+# Use a thin device to provide deterministic discard behavior. Discards are used
+# by the log replay tool for fast zeroing to prevent out-of-order replay issues.
+_test_unmount
+_dmthin_init $devsize $devsize $csize $lowspace
+_log_writes_init $DMTHIN_VOL_DEV
+_log_writes_mkfs >> $seqres.full 2>&1
+_log_writes_mark mkfs
+
+_log_writes_mount
+
+# First create all the subvolumes
+for i in $(seq 0 49)
+do
+	$BTRFS_UTIL_PROG subvolume create "$SCRATCH_MNT/sub$i" > /dev/null
+done
+
+# Then run 100 fio jobs in parallel
+for i in $(seq 0 49)
+do
+	fio --name=seq --readwrite=write --fallocate=none --bs=4k --fsync=1 \
+		--size=64k --filename="$SCRATCH_MNT/sub$i/file" \
+		> /dev/null 2>&1 &
+done
+wait
+_log_writes_unmount
+
+_log_writes_remove
+prev=$(_log_writes_mark_to_entry_number mkfs)
+[ -z "$prev" ] && _fail "failed to locate entry mark 'mkfs'"
+cur=$(_log_writes_find_next_fua $prev)
+[ -z "$cur" ] && _fail "failed to locate next FUA write"
+
+while [ ! -z "$cur" ]; do
+	_log_writes_replay_log_range $cur $DMTHIN_VOL_DEV >> $seqres.full
+
+	# We need to mount the fs because btrfsck won't bother checking the log.
+	_dmthin_mount
+	_dmthin_check_fs
+
+	prev=$cur
+	cur=$(_log_writes_find_next_fua $(($cur + 1)))
+	[ -z "$cur" ] && break
+done
+
+echo "Silence is golden"
+
+# success, all done
+status=0
+exit
diff --git a/tests/btrfs/194.out b/tests/btrfs/194.out
new file mode 100644
index 00000000..7bfd50ff
--- /dev/null
+++ b/tests/btrfs/194.out
@@ -0,0 +1,2 @@
+QA output created by 194
+Silence is golden
diff --git a/tests/btrfs/group b/tests/btrfs/group
index b92cb12c..0d0e1bba 100644
--- a/tests/btrfs/group
+++ b/tests/btrfs/group
@@ -196,3 +196,4 @@
 191 auto quick send dedupe
 192 auto replay snapshot stress
 193 auto quick qgroup enospc limit
+194 auto metadata log volume
-- 
2.21.0